Improved Categories for Puzzles By Type (double-sided, irregular edges, split tendril connectors, etc.)

We have improved our categorization of puzzles by type of design features, so now it's easier to find a good listing of double-sided puzzles, puzzles with irregular edges, and puzzles with different types of pieces. 

We are also working on adding a Puzzles By Piece Count categorization again, that will be linked from the Home page once it's ready.